DESCRIPTION: The in vivo micronucleus (MN) assay is a widely used test to screen compounds for chromosome-damaging activity. It is also a key test for the registration of new pharmaceuticals. Litron Laboratories has developed an automated method of scoring MN using flow cytometry (FCM). This system has several benefits: increased numbers of cells analyzed, ability to process more samples in less time, and objective analysis/scoring. In Phase II work Litron will perform experiments designed to validate their kit for scoring MN. Specifically, they and their collaborators will: analyze genotoxic compounds with different modes of action, perform the entire assay from animal dosing to blood fixation and analysis, perform microscopic evaluations of these same blood samples for comparison with FCM, measure interlaboratory variability, and prepare a document to submit to ICCVAM for regulatory approval. PROPOSED COMMERCIAL APPLICATION: The validation and regulatory approval of Litron's FCM based MN assay would result in increased sales of Litron's developed mouse peripheral blood MN analysis kits. Similar studies are planned for analysis kits to measure MN in mouse and rat bone marrow, rat peripheral blood and also human peripheral blood. Enormous commercial opportunity exists from the sale of these kits.